We will purify Rauscher Leukemia Virus (RLV) DNA polymerase (reverse transcriptase) to homogeneity using affinity chromatography on polycytidylate- agarose, a procedure which we have developed. This method has yielded near-homogeneous preparation of this and other viral polymerases with high yields. The biochemical properties of the RLV enzyme will be fully characterized with respect to DNA synthesis on a variety of synthetic and natural template-primers. The possible involvement of cellular DNA polymerases or other proteins in the synthesis of proviral DNA through the formation of RLV reverse transcriptase-cellular protein complexes will be studied through in vitro complexing experiments and examination of virus-producing murine tissue in order to observe the presence of in vivo complexes. New methods of examining polymerase-template-primer binding will be developed using insolubilized template-primers in order to examine true binding preferences and the effects of reaction components on the binding process. Monospecific antisera will be prepared aginst homogeneous RLV enzyme and used, together with radioactively labeled enzyme, for the development of a sensitive radioimmunoassay for the detection of antigenically related proteins. The radiommunoassay will then be used to detect and quantitate the presence of such proteins in human normal and neoplastic tissues. The above enzymological studies will serve to provide a more complete understanding of the process of reverse transcription, while the immunological aim will serve to determine whether mammalian oncornaviral-like reverse transcriptase is present in all human tissues or may truly be considered as a marker for human neoplasia.